Recently, an effort into reduction of greenhouse gas as a solution for global warming has been globally expanded. In particular, for reduction of emissions of carbon dioxide and regeneration, progress of industrialization of polyalkylene carbonate using a catalyst has been accelerated. The polyalkylene carbonate is a rubber plastic which is soft at room temperature due to unique characteristic, and has significantly excellent processability and excellent decomposition ability. Accordingly, a research into the polyalkylene carbonate as a biodegradable polymer has been actively conducted. However, the polyalkylene carbonate has limitations in being applied to various fields due to a low glass transition temperature (Tg) and easy degradability around 200° C. Accordingly, technology of increasing the glass transition temperature or thermal resistance or improving mechanical strength by blending with various resins has been required. For example, U.S. Pat. No. 4,946,884 discloses a resin composition including a melt-blend of polypropylene carbonate and polymethyl methacrylate (PMMA) or including a binder for molding ceramic or metallic powders, and U.S. Pat. No. 4,912,149 discloses a melt-blend of polyvinylchloride acetate to improve mechanical properties. In addition, Korean Patent Laid-Open Publication No. 10-2013-0124199 discloses an interpenetrating cross-linking composition using a polyalkylene carbonate resin having a high molecular weight of 30,000 g/mol or more. However, the polyalkylene carbonate resin composition has a low molecule unit compatibility, which makes it difficult to achieve a synergistic effect of physical properties by mixing, and has insufficient improvement of transparency and mechanical strength such as robustness, and the like, and therefore, research into a polyalkylene carbonate resin composition for improving the above-described problems has been demanded.